Various devices are known in the prior art which are designed to eliminate the need to dig a hole in the ground in order to anchor a post in an upright, vertical position. For example, U.S. Pat. No. 284,219 which issued to Mehew on Sep. 4, 1883, discloses an anchoring socket for fence posts having a pair of vertical side plates extending upwardly from opposite sides of a base plate. Both side plates have apertures for insertion therethrough of bolts or other fasteners into a fence post placed between the side plates. The Mehew socket further includes a ground-penetrating stud projecting downwardly from the centre of the base plate, and a pair of arrow-shaped pins projecting downwardly from opposite sides of the base plate for anchoring the socket in the ground.
The primary drawback to the Mehew design is its relative instability. In particular, the surface area of the Mehew socket base plate is roughly equal to the cross-sectional surface area of the post to be supported. Since the weight of the post is supported by a relatively small foundation, the Mehew socket is not able to effectively resist twisting forces acting on the post, such as wind sheer. Although the Mehew socket may be suitable for small fence posts (which are also braced by siding extending between adjacent posts), it would not be suitable for anchoring relatively heavy highway sing posts and the like.
U.S. Pat. No. 396,624 which issued to Thomas on Jan. 22, 1889, discloses a post holder consisting of a socket mounted on a rectangular base plate having a surface area substantially larger than the post cross-sectional area. However, only a single, central ground-penetrating shaft extends downwardly from the base plate and hence no significant increase in post stability is achieved. Although Thomas indicates that his base plate may include openings through which stakes may be driven to hold the socket more firmly in position, this would significantly increase installation time.
U.S. Pat. Nos. 3,809,346, 4,156,332 and 4,644,713 disclose various other post anchoring devices designed to eliminate the cost and labour of preparing post holes, and to prevent the rapid deterioration of posts supported in such holes. However, none of the above-noted references teach the combined advantages of (a) supporting a post on a base plate having a surface area substantially larger than the post cross-sectional area and (b) providing a plurality of ground-penetrating stabilizing pins integrally connected to the base plate and spaced around its perimeter for enhanced stability.
Further, the prior art does not reveal anchoring devices specifically adapted for supporting hollow plastic posts which are becoming increasingly prevalent due to cost and safety factors.